RichardGee

My Feedback: (156)

Bob,
I was afraid you might say that.. Indeed my gearhead side comes to exactly the same conclusion - [] DON'T FLY[X(]
And your theory would be dead-nuts on the mark IF I hadn't continued cleaning, and crying, and delving into this problem... I believe I found the ROOT CAUSE:

The ignition cable is burned from being up against the exhaust manifold. See picture!
And yes, I KNOW the instructions say to keep it AWAY from the manifold, but evidently my routing was FAULTY[X(]
WORD TO THE MUCH WISER NOW!!!

No doubt the ignition cable was shorting up against the exhaust manifold and the on/off/misfiring of the engine created enough vibration to break the exhaust outlet.

Looks like my Moki will be making a trip to the service man... is TBM our only option at this point???

JRSmith

My Feedback: (47)

Vogelsang Aeroscale is also a US repair facility for Moki engines to the best of my knowledge. Take care and all the best.

http://www.vogelsang-aeroscale.com/index.html

Jason

mogman

I obtained the flex exhaust tube from aircraftinternational.com.

WARBIRDRCER

My Feedback: (22)

My guess is that what may have appeared as a rough running engine could have been caused by the sound of the exhaust from the cylinder firing through the damaged collector ring.

Questions:

Do you dead stick the airplane in?

If not, could you control the throttle during the landing?

If not, was the engine vibrating hard when you landed?

Did you have any backfiring through the carburetor? If yes, you could have had an intake valve sticking open during a firing sequence.

Did you have misfiring through the exhaust? If yes, you could have had an exhaust valve sticking during the firing sequence.

Have you conducted a valve lash check? If so, did any valves have excessive clearances with the rocker arm tips?

With a solid state ignition, I am less suspect of vibration causing misfiring of the plugs. Your ignition module was less likely to be vibrating unless the engine was rough running anyhow. These engines and normal flight operations do not cause a lot of tossing and banging of the airframes. Plus other primary components of the ignition system are located on, or inside of the engine, i.e. the pick-up (hall) sensor and ignition capacitors. (See attached photo)

Concerning the vibration causing the damaged collector ring. The collector ring is hard mounted to the engine via the intake tubes and exhaust headers. If the exhaust was allowed to move independent of the engine I could see this happening.

Questions:

From your photo it is hard to tell, but is there any signs of damage to the base of that cylinder or loose cylinder base hardware?

Are there any signs of cracking from other exhaust headers? You may locate small cracks by exhaust tracks emanating at the welds.

Check the engine mount for cracking or damage.

I would recommend checking the valve clearances, securing your ignition module, check all engine hardware for security, reinstall your collector ring, and test run.

I hope this helps you.

WARBIRDRCER

My Feedback: (22)

Great find, and good trouble shooting.

RichardGee

My Feedback: (156)

THANKS for all the detail.
I got VERY LUCKY on this one as not only was I able to land the plane with a live engine (albeit somewhat sick), it did not take too long to find the root cause of the problem.
Looks like I will be packing it up and sending to Vogelsang.

WARBIRDRCER

My Feedback: (22)

Post some shots of the P-47. Would like to see it. Like you, I am a gearhead myself and enjoy helping others with their troubleshooting. I always learn more by seeing what others are doing. Like Bob's engine montoring system. I never knew they had those for models. I have installed several JPI systems in full scale aircraft, but never a model. However, they are worth their weight in gold.

You will be pleased with VA, Gotz and Steve are great.

Hope you make the warbird event.

RichardGee

My Feedback: (156)

You can see my Thunderbolt here:
http://www.youtube.com/watch?v=lFYnvJnaBpk

77chickenhawk

that wind sound is killer on the ears.lol

WARBIRDRCER

My Feedback: (22)

What a great looking Warbird. The video is very well done. I like the special effects you used. Everyone, be sure to sit back, relax, and let it play.

Its looks like a real stable airframe. The wind appeared to be across the runway somewhat, but the plane was handled by you superbly.

Thanks for the video,

Steve

Axle Al

My Feedback: (25)

you say you have several moki's and a few 400's so how many do you have? several? and now you need advice ? sounds like you should be giving advice. what is wrong with this picture?

ram3500-RCU

My Feedback: (221)

Beautiful Jug. Hope you don't miss too many events with her. What a treat to watch, (and hear). Thanks.

I have seen the Meister P-47 fly with a Moki 150 several times. Seems like the same performance just on a little smaller scale. Great combination.

nine o nine

My Feedback: (1)

Axel Al, Scott originated this thread so he could learn more about these engines as well provide a place for everyone else to do so as well. Yes, he has several of these engines and if you'd see him operate them you'd be impressed rather than doubtful. I'll leave it at that. Mitch

GaryM

My Feedback: (14)

Hey Scott,

Any pics yet of the 400 mounted on the 12 ft. P47 or just some up on all three wheels so we get the ideal of how huge this thing really is.

Thanks for having started this thread so we can all share our expierence and advice with one another to keep our Mokis running smooth and reliable.

WARBIRDRCER

My Feedback: (22)

Roger That and Agreed!! Thanks Scott

RichardGee

My Feedback: (156)

Just an FYI... I flew the JUG all weekend with one broken collector ring exhaust stack and NO ISSUES.
The ignition cable repair seemed to hold up well also.
Engine just kept on truckin
Just wish the BLACK GOOO would stop pouring out of the carb pump unit at the front of the engine... what a mess![X(]

Scott Prossen

Hey Gary and Warbirdrcer,

I think this is what you are asking for. I have posted some pictures on this thread so as not to muck up the MOKI thread. Thanks for looking and asking. Hope this satisfies the curiosity???

Scott

http://www.rcuniverse.com/forum/m_10..._6/key_/tm.htm

Blackwidow

Gents,

Ihave been playing around with my new Moki 250 radial for a few weeks now and have some questions and observations Iwas hoping to solicit some help with. Ishould admit Ihave only read about 2/3rds of the posts on this thread so it is possible the answers to my questions may have already been posted and if that is the case I appologize in advance.

My setup:

Ihave the moki mounted on a stand (see image) with a 32x14 Menz prop for break-in. Iam running non-synthetic oil at 32:1 and premium gas. Ihave removed the pressure tube from the crankcase to the carb and plugged it on both ends. I have installed the electric fuel pump. I have set all the rocker arms to 0.007" gaps and all spark plugs to 0.014" gaps. Iam running a 7.4VLi-Ion ignition battery with a 5.2V regulator that is powering both the ignition module and the fuel pump.



Questions / Observations:

1) Can somone post their starting proceedure both for first runs and subsequent runs in the same day? Iam used to 3W, Zenoah and DA gas engines. With those Ihave always opened the throttle full, close the choke and turn on the ignition then prop it until it pops. Once it pops you reduce the throttle to a high idle position, take off the choke and prop it another 5 - 6 time and they always start. For subsequent starts during the day there is no need to choke the engine just go to high idleturn on the ignition and start the motor. With the MokiIam finding that the same choke process works for the first start of the day but subsequent starts are giving me fits. That is to say the motor is hard to start after the first run. Do you guys choke your on every start? Maybe I'm flooding it but Iam having a tough time getting it start again after the first run of the day.

2) What are the two green LEDs indicators on the ignition module? Ialways get one green LED whenever the ignition switch is turned on but the second one sometimes is on and sometimes is not when I turn on the ignition and I'm not sure what that is telling me.

3) My exhaust manifold nuts are continually loose after each run. Is there some proceedure such as tightening them while hot or some high temp loctite or wiring them to prevent them from coming loose in flight?

4) Ihave seen a few posts that indicate one cylinder being cooler than the rest and I am seeing the same thing. What I call number 4 (looking at the crankshaft the cylinder at about 7 o'clock) will consistently run about 50 degrees F cooler than any of the others with cylinder #1 (12 o'clock)running the hotest by about 20 degrees F. The other cylinders (#2 #3 &#5)all are within a few degrees of each other. Anyting to worry about here?

Well....I think those are the largest questions and issues Iam having.

Thank you to all the contributors to this thread!!!!!! As you all know the documentation for such a high end motor is pretty sparse and this thread is really helpful to us just learning how to interface with this motor.

Tom

JPate147

Hi Tom,

I am no expert, but with the help of this thread I have been able to get both my Moki 250's to run smooth. I will give you my experiences in the same order as your questions:

1) If the engine has cooled between flights, I always re-choke the engine until it pops. They always choke with 4 flips and start with four more after opening the choke and reducing throttle trim.

2) I don't know what the lights indicate other than 'ready'.

3) I have tried the hi temp loctite with no success. I have to tighten my exhaust nuts after every two flights.

4) The different cylinder temps have to do with the fuel distribution inside the crankcase. My engines both have number one the most hot, with varying temps on the others.

On your attched photo, the fuel pump does not seem to have the small blue feed lines that come with the pump. There is also a small crossover (return) line that is pre-plumbed by the factory. Did you remove these or they just obscured in the photo?

TJPro351

My Feedback: (8)

Hi Tom,
As others would state, I am no expert either but I do question running non synthetic oil during breakin. I always thought that Goetz and/or TBM (Mike Dooley) states to start out with synthetic oil during breakin mixed at 32:1 for the first two gallons, then go to 40:1 for another two gallons and the final mixture is 50:1. I know some others run 40:1 synthetic right from the start and after 5 gallons, go to 50:1.
I believe the two green indicators on the ignition will alternate depending on prop (cylinder) position. I have seen one or the other on during starts but not at the same time. I too have to re choke AFTER engine cools down for the next flight. I too am trying to figure out what can be done to stop the exhaust nuts from coming loose every time we fly. I have seen others drill and tap a set screw in to stop the nut from turning. The cylinder temps are "normal" and I have heard that with using the electric pump and the turbolator gets all the cylinders within plus/minus 5 degrees.

Agree, great thread to get answers and learn!

Tim

germrb

My Feedback: (3)

Tom,

Welcome to the wonderful world of radials. Most of your comments are very typical.

1. You've got the correct starting procedure for first of the day starts. Subsequent starts depend on the engine temperature. If the engine has cooled significantly, recoking is going to be required most frequently. Normally, if the engine is still up close to operating temperature, one or two flips should get you going again.

2. The lights on the ignition module indicate two things. One lights, which is always on, is ignition power indication. The second light is a firing indication. If you happen to stop on a firing location, both lights will be on. One way to check your ignition module is to apply power and slowly rotate the prop 360 degrees and verify that the firing sequence is operating on all cylinders. Be careful and be sure that you have a firm grip on the prop at all times.

3. I have not found an acceptable solution to the loosening of the exhaust manifold nuts. I have never had one come completely off or any ill effects from them being loose. We all know that nuts are suppose to be tight, its annoying.

4. One of the short comings of radial engines is uniform cylinder performance. The other gentleman's comments about fuel distribution are true. The cool cylinder you are referring to is the #3 cylinder and it is always the coolest. Even to the point of shutting down because of excess fuel/oil mixture. Using a non-synthetic at 32:1 is fine for the first gallon or so, but you quickly want to go to a high grade synthetic at 50:1 for flight. The high oil consentration will shut down the #3 cylinder resulting in rough performance. When it happens you will recognize a distinct change in engine performance. A gentleman named Detlef Kunge in Germainy makes a "turbulator", which improves the overall fuel distribution within the intake manifold. They are available from Vogelsang. Unless you happen to have a particularly tempermental engine, I'm not sure I would go for the additional installation complexity.

One other thing, don't block the pulse pump on the front of the engine or the carb diaphram port. Just remove the tube from the Festo fitting and the carb.

Every engine is a little different, so keep running yours until you recognize its normal behavior.

Good luck,

Blackwidow

JPate147, TJPro351 and germrb,

Thank you for your responses!!!!

It helps to know more about what it takes to keep these motors happy.

Jpate147 - Ihave the blue feed lines that came with the pump and plan to use them on my Waco but Iguess when I read that they needed to be cut off once installed I thought I didn't want to deal with that on a test stand so I just used Tygon. As for the Tee no Idon't have one. The documentation Ihave seems to show two different models of the pump. One with only two nipples where there is both a crossover and a tee to provide an overflow return to the tank. However my pump has three nipples two of which are identified by an arroww showing flow direction IN - OUT and the other is marked R for return to the tank.

Thanks again guys!

RichardGee

My Feedback: (156)

What is the typical engine running time required before:
- Pulse pump grease STOPS coming out and running down the engine?
- Pulse pump mechanism is DRY and must be re-greased?

Thus far I have found that engine performance declines as the day wears on, with flights 3 and 4 experiencing harder starts and more irratic engine performance.

Engine runs beautiful for flights one and two. I do clean pulse pump tube and lightly oil rocker valve actuation mechanisms before each outing, but grease really comes out of the pulse pump if I push the engine hard through a couple tanks of gas.

Running Yamalube R (synth), 50:1, and premium gas.
http://www.youtube.com/watch?v=8i9pTrbO67E

germrb

My Feedback: (3)

Rich,

First of all, very nice video.

I know you don't believe that a fuel pump is necessary, but it does eliminate the dirty pulse pump tube problem. Its difficult to tell how long the grease will last. The last time I talked to Mike Dooley I seem to remember that it wasn't a periodic maintenence issue. You might check with Mike on that subject. I have always had some residual grease at the pump, whcih requires an occasional wipe down.

The deteriorating performance later in the day sounds very much like heat build up. If your cylinder head temperatures are staying in the range of 240 or below, then its something else. I have onboard temperature sensors with full baffles and still have trouble keeping #1 cylinder temperatures under control. The times I have been running hot, the engine performance kept getting worse in the later flights; as well as more and more difficult to start. Just a thought, maybe its something else.

Good luck,

RichardGee

My Feedback: (156)

Bob,

I tend to agree with your theory on engine temps getting too high. But why would this cause a starting problem if the engine has cooled for an hour between flights? My engine DOES in fact get harder to start later in the day which I assumed was grease in the pulse pump tube. However, never have I serviced the tube at home and found that it was clogged. I can always blow throught it easily. It just gets all black inside. I clean it until it is clear.

Have you heard of guys cooking a cylinder due to high temps just from running hard? My engine seems to be tuned perfectly at all RPMs so I would not suspect a lean condition. I did take a cylinder temp reading immediately after one flight and all cylinders were under 240 degrees F.

I may go to a pump yet. I also like the idea of more even cylinder temps promised from a Turbolator, but cylinder baffling might be a better way to achieve this?